1. Field of the Invention
The present invention relates to a drive force transmission device for driving a driven portion of a camera.
2. Description of the Related Art
Conventional drive force transmission device for a camera, which has been previously proposed in Japanese Unexamined Patent Publication No. 8-304894 Official Gazette, is intended for use in a camera incorporating a drive mechanism adapted to select and drive a plurality of driven systems. In the aforementioned camera, a drive force from a drive source is selectively transmitted to winding means or rewinding means through a drive mechanism constituted by a plurality of connected gears.
However, in the case of the aforesaid conventional drive force transmission device disclosed in Japanese Unexamined Patent Publication No. 8-304894 Official Gazette, it is necessary for transmitting to place a plurality of gear transmission systems constituted by spur gears therein. Thus, necessary space increases, so that it is inevitable to increase size. Moreover, when reducing the sizes of the gears so as to downsize the camera, the transmission efficiency of the device is degraded. Further, the number of parts or components increases. Thus, such a camera is disadvantageous due to the cost thereof. Therefore, the conventional drive force transmission device has encountered such serious problems in optimization of gear placement.
Hitherto, power transmission through a gear train composed of spur gears has been generally used. However, in the case that there are a plurality of transmission paths which are long, there are too many gears to be contained in a camera. Consequently, the conventional drive force transmission device has a disadvantage that the transmission efficiency is deteriorated.
Further, conventional drive force transmission devices for cameras, which have been previously proposed in Japanese Unexamined Patent Publication Nos. 6-347876 and 7-43801 Official Gazettes, respectively, are intended for use in film feeders of cameras. Thus, the lead angles of helical gears of the drive force transmission system are set at predetermined values, respectively. Moreover, it is realized that both a spool gear and a winding gear for film are driven according to the magnitude of the drive force from the drive source, alternatively, the spool gear and the winding gear are selectively driven according thereto.
However, the aforementioned drive force transmission devices disclosed in Japanese Unexamined Patent Publication Nos. 6-347876 and 7-43801 Official Gazettes, respectively, employ a mechanism in which two rotary shafts are coupled to each other or uncoupled from each other in a line. Thus, the conventional drive force transmission devices have an inconvenience in that a space, in which the rotary shafts move, is needed, and that furthermore, the lateral size of the camera is increased. Moreover, the helical gear should be designed so that two rotary shafts are coupled or uncoupled in a line. Additionally, two rotary shafts are coupled and uncoupled Therefore, it is necessary to enhance the accuracy of the helical gear and a gear to be engaged therewith. Furthermore, it is necessary for preventing the degradation in transmission efficiency to enhance the accuracy of each coupling portion for coupling the two rotary shafts. Consequently, the conventional drive force transmission device is disadvantageous due to cost thereof.